Web3.js is a library specifically designed for Ethereum, primarily used for interacting with the Ethereum blockchain, such as sending transactions and interacting with smart contracts.
Web3.js does not directly support Bitcoin. Bitcoin has its own set of APIs and libraries, such as Bitcoin Core, BitcoinJS, or Bitcore.
If you need to handle both Bitcoin and Ethereum in a project, you may need to use two different libraries: for example, use web3.js for Ethereum-related functionalities and BitcoinJS for Bitcoin-related operations.
An example application scenario could be developing a wallet that supports multiple cryptocurrencies. In this case, you can use web3.js to manage users' Ethereum transactions and smart contracts, while using BitcoinJS to handle Bitcoin sending and receiving. This ensures that your application can effectively interact with both major blockchain technologies without worrying about library compatibility issues.